1. Field of the Invention
The present invention relates to a method of lubricating and cooling a hydrodynamic plain bearing for a rotating element, which bearing has at least one fixed gliding plane, and a pressure chamber and a decompression chamber are arranged upstream of the gliding plane, wherein a fresh, cold lubricant is supplied under pressure from the pressure chamber to a lubricating gap between the rotating element and the fixed gliding plane at an entry end, the lubricant supply being so controlled that a sufficient lubrication wedge is created between the rotating element and the gliding plane, and used, hot lubricant is removed therefrom at a discharge end of the gliding plane and is conducted from the lubricating gap into the decompression chamber, any hot lubricant adhering to the rotating element being partially moved into the decompression chamber and fresh, cold lubricant being supplied under pressure from the pressure chamber in a subsequent lubricating gap.
This invention also relates to a plain bearing with fixed gliding surfaces for a rotating element, such as a cylindrical shaft or a pressure disc, with means for supplying the fresh, cool lubricant under pressure.
The invention deals with plain bearings for rotating elements gliding in the bearing at high speeds, such as gas and steam turbines, turbo-compressors and turbo-gears connected therewith. The plain bearings of the present invention are designed for rotating elements gliding at high speeds in the bearings, in a chamber filled predominantly with gas, for example a gearbox or bearing box of a turbo engine filled predominantly with gas.
2. Description of the Prior Art
It is known from U.S. Pat. No. 3,680,932, particularly FIG. 12, to provide a hydrodynamic journal bearing for large machines, such as turbines and generators. The load-bearing lower part of the bearing extends over and angle of about 160°. The upper half of the bearing is not subjected to any load, and there is a half-moon-shaped space between the shaft and the inner surface of the bearing. This bearing has three gliding segments arranged between two grooves associated with each gliding segment. In this arrangement, the foremost groove, in the direction of rotation of the shaft, constitutes the pressure groove and the groove at the end of the gliding segment constitutes the decompression chamber. Fresh lubricant is pressed under pressure from the pressure groove into the space between the rotating shaft and the gliding segment and is taken along by the rotating shaft to the decompression groove. The used, hot lubricant is removed from the decompression groove. The pressure groove of the gliding segment downstream of the decompression chamber, in the direction of rotation of the shaft, is spaced from the preceding decompression chamber, the spacing being sufficient to prevent lubricant from the pressure groove to flow into the adjacent decompression chamber. The pressure and decompression grooves are flat and fully filled with lubricant. Therefore, the entire inner surface of the bearing is filled with lubricant, i.e. all the pockets and grooves of the bearing. In such a flooded bearing, the lubricant exchange proceeds in a mixing chamber, as is shown in accompanying FIGS. 1 and 2 illustrating the state of the art.
The journal bearing disclosed in this patent is completely covered by the lubricant and has a relatively high loss factor, the losses of such lubricated bearings rising with proportionally with the surface covered by the lubricant.
Known bearings for shafts rotating at high speeds include the offset-half structure, the double-offset structure, the hybrid bearing, the so-called lemon play bearing, the multiple-plane bearing with two to five sliding planes, and the axial bearing with wedge planes for one or two rotational directions.
In the offset-half bearing structure, an upper gliding plane is offset horizontally from a lower gliding plane by a predetermined distance so that the shaft circumference contacts the bearing along two different lines. The two gliding planes are coaxially offset relative to each other and to the axis of the shaft. In the double-offset bearing structure, the two gliding planes are offset relative to each other horizontally as well as vertically. In both structures, the lubricating gap forms a wedge tapering in the direction of rotation of the shaft.
In the hybrid bearing, a lower fixed gliding plane is combined with an oppositely positioned pivotal gliding plane.
The so-called lemon play bearing is a variation of the multiple-plane bearing.